Firefighters continued to fight flare-ups and damp down hotspots from a large blaze on Great Barrier Island on Thursday ahead of more hot, windy conditions predicted over the weekend.
The Defence Force and police have joined forces with local and national fire crews to contain the fires in the Hauraki Gulf. Crews will continue work until nightfall and resume at dawn on Friday.
The fire began on Tuesday morning and has burnt though 100 hectares of scrub and bush on the eastern side of the island.
Glyn Walters, an Auckland Council spokesperson for authorities working on the island, said changes in heat and humidity have caused some flare-ups on Thursday afternoon.
Forty-five volunteer rural firefighters are continuing to beat back fires along the containment perimeter and a helicopter remains on the island to support crews.
Mr Walters said firefighters are working on strengthening containment lines before Friday, when hot weather and winds are expected to pick up and continue until Monday and could cause the fire to spread.
"We've got no rain forecast for the next two weeks in the Auckland region. We really need to make as much progress as we can today with this low wind speed and try and extinguish all the hotspots.
"We'd like people generally in the Auckland region to be careful at the moment. We are in a restricted fire season and everybody needs to be careful around the use of any fire."
Mr Walters said an independent fire investigator on Thursday will try to establish how the blaze started, while specialists will give firefighters advice on where it could flare up again.
Claris airport has closed its flights, but Okiwi airfield is operating on Thursday.
Residents from Okupu Ridge returned to their homes on Wednesday.